Diagnosis and Performance Monitoring - Deploying and Managing a Cloud Infrastructure - page 138

Cloud computing relies on data and therefore large amounts of storage. Cloud computing
providers often have large storage area networks with a massive number of storage servers.
And there is a requirement that all users be able to access such resources quickly and consis-
tently, so failover protection and redundancy are very important.
With data growing exponentially, especially with entertainment media going digital and
high-definition videos becoming the norm, video streaming providers need powerful network
interfaces to their storage in order to provide files quickly. Multipathing is an effective way
of increasing the available bandwidth to Internet Small Computer System Interface (iSCSI)
networks, much like bonding does for normal networks. In multipathing, multiple physical
paths are used between hosts and data storage devices in case there is any link failure in the
SAN network such as ones caused by faulty NICs, switch, or cables. The software can simply
switch to another physical path, which circumvents the failed components. This is known as
path failover.

FIGURE 5.5 A simple representation of the multipathing concept

Source machine

Routers Data stores

Load Balancing

Cloud computing services are used by thousands of users at once, enterprise customers as
well as individual users. But the promise of virtually unlimited resources is still largely a fan-
tasy, the ideal scenario. The truth is that resources are very, very finite and being shared by
hundreds of thousands of people. The reason that everything—every server, every switch—
doesn't just stop working that some ingenious resource management methods are used. Load
balancing is one of these methods. A load balancer, usually just another server, assigns con-
nections and requests to different servers, making sure that not one server is overloaded. This
is essential in making things run smoothly.

Scaling: Vertical vs. Horizontal vs. Diagonal

Scalability is often one of the main aspects and reasons that companies are moving their
infrastructures to the cloud. It makes sense because it is easier to scale and expand in a virtual
environment when the number of servers you can deploy is no longer limited by the size of